As for a plasma processing apparatus for manufacturing a semiconductor device, there is widely used a so-called parallel plate type plasma processing apparatus which includes a lower electrode for mounting thereon a substrate such as a semiconductor wafer, a liquid crystal substrate or the like; and an upper electrode disposed to face the lower electrode in a processing chamber. In this plasma processing apparatus, the substrate is mounted on the lower electrode, a processing gas is introduced toward the lower electrode through a multiple number of discharge holes formed in the upper electrode, and then plasma of the processing gas is generated by applying a high frequency power between the electrodes. Accordingly, a plasma process such as an etching process or a film formation process is performed on the substrate.
In this parallel plate type plasma processing apparatus, a distance between the upper electrode and the lower electrode may affect plasma processing characteristics on the substrate. Therefore, the distance needs to be accurately adjusted depending on processing conditions or types of plasma processes. Especially, when different types of plasma processes or plasma processes having different processing conditions are continuously performed in the same processing chamber, the distance needs to be adjusted to an optimal distance for each of the plasma processes. For this reason, conventionally, there has been developed a plasma processing apparatus capable of optimally adjusting a distance between an upper electrode and a lower electrode by vertically moving the upper electrode (see, e.g., Patent Document 1).
The plasma processing apparatus described in Patent Document 1 is configured to vertically move the upper electrode between a ceiling wall of a processing chamber and the lower electrode by installing the upper electrode at the ceiling wall of the processing chamber via a bellows. With this configuration, the distance between the upper electrode and the lower electrode (distance between electrodes) can be adjusted by vertically moving the upper electrode.
Patent Document 1: Japanese Patent Laid-open Publication No. 2005-93843
However, in the above-described conventional plasma processing apparatus, since the bellows is installed above the upper electrode, a gap of a certain height exists even when the bellows is contracted. Therefore, a space (space above the upper electrode) between the ceiling wall and the upper electrode is formed within the processing chamber. As a consequence, a processing gas supplied into the processing chamber may also be introduced in this space through a gap between a side surface of the upper electrode and an inner wall of the processing chamber and remain therein.
The processing gas introduced in this space may be hardly exhausted even by driving a vacuum pump. By way of example, when the upper electrode is moved vertically or when an internal pressure of the processing chamber is controlled for a next plasma process, the processing gas remaining in this space may flow downward toward a processing space below the upper electrode. This may affect plasma processing characteristics. Further, when the processing gas is introduced into the space above the upper electrode, a pressure may be increased. Hence, abnormal electric discharge may occur in the space when a high frequency power is applied between the electrodes.